A cryogenic microfluidic cooling system that can cool MRI surface coils to liquid nitrogen temperature without affecting the temperature at the imaging surface, while maintaining minimal distance between the coils and the target samples for maximum sensitivity will be developed. Conventional cryostats used to improve coil sensitivity require a thick insulating layer between the coil and the sample and are not applicable to surface coils that typically have relatively shallow penetration depth. Therefore, a cryogenic cooling system that can keep the surface coil and the sample in close proximity for maximum coil sensitivity can prevent the SNR loss associated with thick cryostats and therefore provide significantly higher SNR than un-cooled coils. Microfabrication technology will be used to develop a microfluidic cryo-cooling system with integrated surface coils to cool the coil with minute (nanoliter) amount of liquid nitrogen. Temperature profiles at the surface coil and the imaging surface of the developed system will be evaluated followed by characterizing the parameter space of conductor length and geometry. The ability to parallelize the system to surface coil arrays will be also characterized. The system will be evaluated and optimized using MRI and the cryo-cooled surface coils will be compared to un-cooled surface coils. If successful, this will enable cryo-cooling of planar surface microcoils for high-resolution biological sample imaging without the need for a thick conventional cryostat. The resulting system is expected to have an improvement of a factor over 5 in signal-to-noise ratio (SNR) with a potential to reduce scan time by a factor of 25 with no loss in image quality. The significance of the proposed research is that the resulting system can provide critical tools for the current imaging needs, such as imaging small targets (e.g. single cells) by using high-density surface coil arrays or ultra-fast imaging for monitoring real-time physiological changes in biological samples such as blood vessels or brain slices. The developed microfluidic cryo-cooling technology is not limited to a specific surface coil configuration but can be applied broadly to various other planar and non-planar microcoil configurations. This work can be expanded further to cool high temperature superconducting (HTS) surface coil arrays using liquid nitrogen to further improve scanning time without affecting the biological samples to be imaged. This project seeks to develop a microfluidic cryo-cooling system integrated with MR surface coils for high- resolution MR imaging of biological samples. [unreadable] [unreadable] [unreadable]